1. Field of the Invention
The present invention relates to a multiparty calling method and a corresponding mobile communication terminal, and more particularly to a multiparty calling method and corresponding terminal that prevents one party from being disconnected in a multiparty call when another party is disconnected due to a network error, for example.
2. Description of the Related Art
General communication networks, such as the Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), and Universal Mobile Telecommunications System (UMTS) networks, allow a subscriber to simultaneously talk with a plurality of other people using one call channel via a multiparty call service provided by the corresponding network. The multiparty call service is also referred to as a multiparty call (e.g., MPTY Call) or a conference call.
In more detail, FIG. 1 is a flowchart illustrating a related art multiparty calling method among three users. As shown, a first user is speaking via the terminal with a second user (S110), and a third user calls the first user (S120). The first user then places the second user in a hold or stand-by state (S130), and accepts the call from the third user (S140). The first user can place the second user on hold by pressing, for example, the keys ‘2+Send’ on the terminal. The key sequence ‘2+Send’ is generally used to perform various operations such as Hold and Accept, Hold and Retrieve, etc., and in this example, the command is used to perform the Hold and Accept function.
The first user then sends a multiparty call join command via a facility message to the corresponding network providing the multiparty calling service (S150), and receives a facility message (e.g., MPTY OK) indicating the multiparty call join command has been accepted (S160). The facility message is a message including different commands that may be transmitted to and from the network and is defined in the Third Generation Partnership Project (3 GPP) Standard, the entire contents of which is hereby incorporated in its entirety. Upon receiving the multiparty acceptance message, the multiparty call among the first, second and third users is established (S170).
In the related art multiparty call performed as shown in FIG. 1, if the first user receives a disconnection message related to the third user and a sufficient amount of time has passed since the multiparty call was established, the third party call is normally released and the remaining call between the first and second parties is not adversely affected.
However, if the first user receives a disconnection message related to the third user during a shorter predetermined time (e.g, about two seconds) after receiving the MPTY OK facility message, the connection between the first and second users may be closed. The reason this connection may be closed will now be explained with reference to FIG. 2, which is an entity model of a general multiparty call service.
In more detail, if the first user receives a disconnection message 240 within a predetermined time after receiving the facility message (MPTY OK), a call control (CC) entity 200 of the mobile terminal receives both the facility message 230 and the disconnection message 240. The disconnection message includes an exception cause value such as a ‘temporary failure’ with respect to the call connection between the first and third users.
The facility message 230 is then transferred to a supplementary service (SS) entity 210 to be decoded. Then, the decoded facility message is transferred to an upper entity 220. On the other hand, as shown in FIG. 2, the disconnection message 240 is directly transferred from the CC entity 200 to the upper entity 220. Accordingly, in this instance, the upper entity 220 processes the disconnection message 240 before the MPTY OK facility message 230. As a result, the call connection between the first and third users is disconnected.
Further, after receiving and processing the disconnection message 240, the upper entity 220 generates a tone for a predetermined amount of time to indicate the first and third users are disconnected. After generating the tone, the upper entity 220 transfers a disconnection event to an upper User Interface (UI) level (not shown). In addition, while generating the tone, the upper entity 220 receives and processes the MPTY OK facility message 230. Thus, the standby connection between the first and second users is re-opened and placed in an active state allowing the first and second users to communicate. However, when the tone generation is completed and the disconnection event is transferred to the UI level, the audio path between the first and second users is closed, thereby also disconnecting the first and second users.